Sheet guiding apparatus



April 30, 1968 G. P. KNAPP 3,380,637

SHEET GUIDING APPARATUS Filed Oct. 4. 1965 7 Sheets-Sheet 1 FIG. 3

INVENTOR. GEORGE P. KNAPP M,M&W

ATTORNEYS April 30, 1968 Filed Oct. 4, 1965 FIG. 4

G. P. KNAPP SHEET GUIDING APPARATUS '7 Sheets-Sheet 2 FI 52 Kb a 1 36'-J 38 2 I 44 4 Lme :23 $2 T 34 24 1 HMO Angular Velocity T Error in WebPosilion TiH Angle FIG. 6 L

Error in Web Position INVENTOR. GEORGE P. KNAPP MQWU XW ATTORNEYS April30, 1968 cs. P. KNAPP SHEET GUIDING APPARATUS 7 Sheets-Sheet 3 FiledOct. 4, 1965 mZON 04mm INVENTOR. GEORGE P. KNAPP BY NOLLlSOd 83M NIaouaa M,M3

ATTORNEYS April 30, 1968 G. P. KNAPP 3,380,637

SHEET GUIDING APPARATUS Filed Oct. 4. 1965 7 Sheets-Sheet 4 FIG. 8 I04INVENTOR GEORGE P. KNAPP ATTORNEYS April 30, 1968 Filed Oct. 4, 1965FIG. [0

G. P. KNA PP 3,380,637

SHEET GUIDING APPARATUS 7 Sheets-Sheet 5 FIG. 9

FIG. H

AIR

INVENTOR GEORGE e KNAPP BY,

ATTORNEYS April 30, 1968 G. P. KNAPP 3,380,637

SHEET GUIDING APPARATUS Filed Oct. 4, 1965 7 Sheets-Sheet 6 I98 I98 |90I90 5 I34 BO I30 I94 I'll/IA |9| H96 200 200 I92 & mg 202 NR 206 FIG. l22:4 nov 2'4 INVENTOR GEORGE I? KNAPP ATTORNEYS April 30, 1968 G. P.KNAPP 3,380,637

SHEET GUIDING APPARATUS Filed Oct. 4, 1965 7 Sheets-Sheet '7 ATTO R NEYS United States 11 Claims. ((1 226-20) ABSTRACT 6F THE DECLOSURE Asheet guider operating with reduced over-corrective hunting. A guideroll is tilted rapidly to a fixed angle when the guided sheet isdisplaced from a predetermined path, without reference to the extent ofthe displacement, and is snapped back to a neutral position as soon asthe sheet is restored to its path. In one form the ends of the roll areindependently movable by separate actuators, the inactive end remainingstationary. The actuators are preferably double-acting types which applya uniform driving force both on tilting and restoration to minimize thetime delays. A slower rate of roll tilting than of snap return to theneutral position is an optional feature for further reduction ofover-correction of small displacements.

Background and szmzmary of the invention This application is acontinuation-in-part of my US. patent application Ser. No. 337,779 filedJan. 15, 1964, now abandoned.

This invention relates to an apparatus useful for guiding moving sheet,web, or strand materials of indefinite lengths including continuousbelts, in predetermined paths of movement, and is useful for handlingvarious materials, including textiles, plastic firms, paper, tire cord,and the like.

Conventional guiders employ one or more rolls which are arcuatelywrapped by a sheet traveling in a direction transverse to thelongitudinal extent of the roll; provision is made to tilt the rollangularly from its normal or neutral position to correct deviation ofthe sheet from a desired path, by producing a crawling movement alongthe roll. This corrective crawling movement of the web takes place at arate which is dependent upon the angle at which the rolls are tiltedfrom the neutral position, transverse to the direction of sheet travel.

The conventional method of control involves detection of the position ofan edge of the sheet, and the production of an error signal when adeviation occurs, in either lateral direction, in excess of tolerancelimits defining an intermediate dead zone of no detector response. Ithas also been conventional practice to utilize actuating means whichproduce tilting movement of the rolls at a very moderate angularvelocity. The characteristic mode of cooperation of these conventionaldetection and actuating means produces a corrective movement whichcontinues to increase the angle of roll tilt so long as the deviationpersists; the angle of roll tilt thus reaches a maximum at a time whenthe deviation has already been eliminated. The roll remains tilted afterthe edge returns to proper position; and only after an over-correctionhas been effected, which shifts the edge beyond an opposite tolerancelimit, does the roll begin to return toward a normal transverseposition. Of course this over-correction causes the roll to tilt in anopposite sense, and so a cycling behavior continues. The delay inattaining the maximum angle of roll tilt implies that any excess tiltbeyond that required to correct an error of a given magnitude isundesirable; and in fact, an excessive tilt would produce atent O3,389,637 Patented Apr. 30, 1968 increased over-correction in theconventional system. But this method necessarily has a huntingcharacteristic, resulting in undesirably rapid wear of the parts throughunnecessarily frequent cycling, as well as a relatively inaccurateguiding action.

A modification of the conventional system provides for a tiltingmovement whose angular velocity is proportional to the magnitude of thedetected error, rather than being of a fixed value. The roll is therebytilted more slowly in correcting a small error than a large one, butagain the roll attains its maximum tilt angle at a time when the correctweb position has already been restored. This method alleviates to someextent the tendency of the system to over-correct, but by no meanseliminates the difficulty, and further entails much more complex, andconsequently more expensive, controls.

It is the primary object of this invention to provide an improved sheetguiding apparatus which affords improved guiding accuracy, and whichreduces the tendency to over-corect sheet position errors. Furtherobjects and advantages of the invention will become apparent as thefollowing description proceeds.

In realizing these objects, I utilize a guiding method in whichdeviation of the sheet edge beyond predetermined tolerance limits isdetected without reference to the magnitude of the deviation beyondthese limits; and a guide roll is moved to a predetermined tiltedposition of a fixed angle, in advance of the arrival at the detectionzone of any sheet region which may exhibit a still larger deviation. Theroll is held in the predetermined tilted position so long as thedeviation continues to exceed the tolerance limit; and is immediatelyreturned with a snap action to a neutral position when the excessdeviation disappears.

Since the rate of corrective movement of the sheet is proportional tothe angle of tilt of the guide roll, correction at a relatively high andfixed rate is thus instituted at once, even though it has not yet beendetermined whether the sheet deviation may be large or small. The rolltilt is always of the same magnitude, subject to adjustment if desired;and depends not on the extent of a sheet deviation, but only on thisdeviation having exceeded the response threshold of the detection means.The corrective movement takes place at a uniform rate regardless of themagnitude of the deviation, the only variable ordinarily appearing inthe process being the duration of the corrective roll displacement. Itis contemplated that the magnitude of the fixed angles of guide rolltilt may be adjusted to a maximum consonant with the ability of a givenmaterial to withstand rapid crawling, but these angles will ordinarilybe held constant for any given application.

According to an alternative mode of operation, the rate of tilting ofthe guide roll from the neutral position is somewhat slower than therate of return. A sufficiently large tilt angle must be provided tocorrect the largest and most rapidly changing errors in web position;however, large errors are relatively infrequent, and the majority ofdeviations are of small magnitude, and change at a slower rate. Someovershoot and over-correction of small errors may result if the maximumtil-t angle is assumed when a minor error occurs, because of the finitetime required for roll displacement. By reducing the rate of tilting ofthe roll from the neutral position, this overcorrective tendency isovercome. If the error is large and persists, the roll reaches itsmaximum tilt angle after a slight delay. In this way, the occasionalextreme errors are corrected largely in accordance with the previouslydescribed procedure, while over-correction of frequent small errors isminimized.

In improved automatic guider apparatus according to a preferredembodiment of the invention, at least one guide roll is mounted forfreedom of movement between a neutral position normal to the directionof sheet travel, and two tilted positions of opposite but equalangularity. The roll axle is received at its opposite ends in guidemeans each affording freedom of movement of one end of the roll betweentwo terminal positions. Either end of the roll may thus be movedindividually and freely between a neutral position and a correctiveposition of one angu lar sense. Separate actuating means are providedfor each end of the roll, and these are adapted to move the roll with arapid snap action between its alternate positions. These means maycomprise electrical solenoids, hydraulic or pneumatic motors, or thelike. I generally prefer that the same actuating means be used to returnthe roll to the neutral position, since the return movement should be asrapid as possible. However, spring means may be used for restoring theneutral position where the equipment has low inertia and can be shiftedrapidly by such means. Spring-return actuators are therefore limited toguiders of small sizes; in larger sizes, the required stroke of theactuating means and the actuating force are correspondingly large, e.g.,6 inches and 100 pounds, respectively. The actuating force for a largeguider calls for springs whose force would vary so greatly over thenecessary length of stroke that performance would be seriously affected.The employment of fiuid pressure or electrical power for bothdisplacement and restoration of the guide roll relative to the neutralposition, gives full actuating force throughout the stroke so that theroll may be restored to neutral in a minimum interval, with acorresponding reduction in over-corrective tendency.

According to a modification, the initial rate of tilting of the guideroll from the neutral position is limited to a lesser value than therate of return, e.g., by restricting the rate of flow of pressure fluidinto pneumatic actuating means, in order to prevent the roll fromattaining its limiting angle of tilt in response to thefrequently-occurring small deviations of the sheet from its path. Sincea small error is quickly corrected, the roll may not reach itsfully-tilted position before being returned to neutral. However, if anerror is of substantial magnitude and persists, the roll continues totilt, attaining its limiting tilted position after a short interval.Provision is made to maintain a maximum rate of flow of pressure fluidto the actuator on the return stroke, so that the roll will be restoredto neutral as promptly as possible upon disappearance of the edgedeviation, thereby restricting any over-corrective tendency to aminimum. To this end, a flow restriction in the fluid supply line to theactuator may be by-passed by a check valve for exhaust and returnmovement, or various other arrangements may be employed, as will readilyoccur to those skilled in the art.

Control of the apparatus may be carried out by any conventionaldetection means capable of sensing a deviation of the sheet beyondtolerance limits in either lateral direction, but these means need notbe capable of detecting the magnitude of the deviation in excess ofthese limits.

While the specification concludes with claims distinctly pointing outthe subject matter which I regard as my invention, it is believed that aclearer understanding may be gained from the following detaileddescription of preferred embodiments thereof, referring to theaccompanying drawings, in which:

FIG. 1 is a pictorial view of an embodiment of the invention in a guideroll structure of relatively small size;

FIG. 2 is a schematic plan view showing the alternate correctivepositions of the guide roll of FIG. 1;

FIG. 3 is a fragmentary view in elevation of a modified form of guideroll support;

FIG. 4 is a schematic view of the guider of FIG. 1, with one form ofdetection and control means;

FIG. 5 is a graphic illustration of the control characteristics ofconventional methods of guider Co t ol;

FIG. 6 is a graphic illustration of the control characteristics of oneform of the improved guider;

FlG. 7 is a graphic illustration comparing the sheetposition correctioncharacteristics of the improved guider and conventional guiders, inrelation to a typical path which might be followed by an unguided sheet;

FIG. 8 is a schematic view of another form of guider of small size,including control apparatus;

FIG. 9 is a fragmentary view in perspective of a modified construction,suitable for guiders of larger sizes, which utilizes double-actingactuating means;

FIG. 10 is a fragmentary sectional view showing a modified form of spoolcontrol valve, providing for the adjustment of tolerance limits, for usein the apparatus of H6. 9;

FIG. 11 is a fragmentary schematic view showing a modification of thecontrol system of FIG. 9, providing ditferent rates of roll tilting toand from the neutral position;

FIG. 12 is a schematic view of another form of guider havingrapid-acting solenoid-controlled spool valves; and

FIG. 13 is a fragmentary view in perspective showing a construction inwhich the guide roll has a fixed pivot at one end.

Referring to FIGS. 1-4, a first form of the improved guiding apparatusis shown, which is preferably of a small size. The guider includes atleast one correcting roll it), which is arranged normally in a neutralposition extending in a direction transverse to the path of movement ofan indefinite length of sheet, web, or strand material 12. The sheet isassumed to travel in the direction shown by the arrow in FIG. 4. As inconventional practice, the roll is wrapped arcuately by the web to asutlicient extent to cause the sheet to crawl laterally over the rollsurface when the latter is tilted at an angle, either in the plane ofthe paper as viewed in FIG. 4, or with a component normal thereto. Theroll is rotatably mounted on suitable bearings (not shown) upon astationary axle 14, whose position is shifted to bring about correctivedisplacements of the roll.

The axle 14 is freely supported in guide slots 16, formed in upstandingmembers 18 of a supporting frame 20, in such manner as to be slidable ineither slot individually. The roll may thus be moved from a neutralposition in which its axis is substantially perpendicular to thedirection of sheet travel, as shown in FIG. 4, to either of twopredetermined titled positions of equal but opposite angle, as shown inFIG. 2. If it is desired to produce a translation to the right of asheet which is moving upwardly in FIG. 2, the roll may be moved toposition 10a; or if it is necessary to translate the sheet to the left,the roll may be placed at 10b.

As shown in FIG. 1, the guide slots 16 are horizontal, and the web is tobe wrapped about the roll in such manner that a vertical plane passingthrough the roll axis will bisect the wrap angle formed between thepaths of approach and departure of the sheet with respect to the roll.An angular displacement of the roll in the horizontal plane, or moregenerally, in a plane perpendicular to that plane which bisects the wrapangle, will produce a reaction in the web which causes it to crawllongitudinally along the roll and thus bring about a lateraltranslation.

However, as is well known in the art, the tilting movement of the rollmay also have a component in the plane which bisects the wrap angle, ormay occur entirely in that bisecting plane, and yet produce the desiredtranslation. Even so, a tilt in this direction will ordinarily alsobring about a difference in the path lengths of the various longitudinalelements of the sheet passing between the guide roll and adjacent rolls.In the case of stretchable materials, this may cause some differentialstretching and distortion to take place; and fragile webs may be torn,or else partially disengaged from the guide roll. The applications forwhich such movements are suitable are therefore somewhat limited.However, they do fall within the contemplation of the invention, and aninclined guide slot illustrated at 16 in FIG. 3 may be used wheredesired, as may be a vertical guide slot.

Actuating means for shifting the ends of the roll individually in theslots 16 comprise a pair of snap-acting solenoids 22, whose armatures 24are linked with the opposite ends of the shaft 14 to drive themindividually in corrective directions upon energization. A preferredform of linkage for each end of the shaft includes a bell crank 26,pivotally mounted at 28 in the support 20. One of the arms of thebell-crank is connected by a pivoted link 33 to the armature 24, and theother drives a roller 32 mounted on the end of the roll axle.

To return the roll to the normal transverse position when the solenoidsare de-energized, compression springs 3-2 are interposed between theaxle and the support 20. As shown in FIG. 1, each of these may comprisea coiled wire spring engaged between a roller 32 and a stop pin 36atfixed to the adjacent support. As shown at the right end of theassembly in FIG. 1, the actuating means associated with either end ofthe roll are encased in a housing 38, only one housing being shown inthe drawing.

The guider also includes detection means shown in FIG. 4 for controllingthe displacements of the roll in a manner to maintain a guided edge ofthe travelling sheet within predetermined tolerance limits of lateraldisplacement in either direction from a nominal position. These meansinclude a pair of electric eye units 36, 38, of conventional type, ofwhich the first is normally shaded by the web and thereforenon-conducting, while the second is normally exposed to a suitable lightsource (not shown) by the guided selvage 40 of the sheet 12 when itoccupies the normal position shown. In this normal relationship, theconducting unit 38 energizes a coil 42 of a normally-closed relay 44, tomaintain its contacts open against the bias of a spring 46, and thusde-energize the solenoid 22 associated with the right-hand end of theroll. The normally non-conducting unit 35, on the other hand, maintainsthe coil 48 of a normally-open relay St'l in a de-ener ized condition,so that the solenoid 22 associated with the lefthand end of the roll isalso tie-energized. The roll is held in the normal position shown, bythe springs 34.

Now, if it is assumed that the sheet exhibits a tendency to travel tothe left as viewed in FIG. 4, so far that the electric eye unit 35becomes exposed to the light source and begins to conduct, the resultingenergization of the coil 4-8 closes the relay contacts 50, and thusenergizes the left-hand solenoid 22 to drive the roll immediately to thetilted position lila of FIG. 2. Of course the unit 38 continues toconduct, and the right-hand solenoid 22 remains de-energized Theresulting tilt will cause the sheet to translate to the right in FIG. 4,returning toward its normal position. However, immediately the unit 36is covered and ceases to conduct, the coil is ole-energized as is theleft-hand solenoid 22, so

that the compression spring 3 instantly returns the roll to the neutralposition shown in FIG. 4.

Now if it is assumed that the sheet exhibits a tendency to wander to theright, the newly-shaded unit 38 ceases to conduct, and the coil 42permits the relay 44 to close, thereby energizing the righthand solenoid22 and causing an immediate tilting movement of the roll to the position1 35 of FIG. 2. This displacement correspondingly produces a lateralshift of the sheet to the left, once again returning it to the properpath, and the roll is then allowed to return once again to the neutralposition.

It will be understood that no attempt is made to maintain the seivage 49in the identical path of travel, but that it is allowed to wanderlaterally within a dead zone defined between tolerance limits, which arephysically determined by the lateral spacing of the electric eye units36 and 38. These limits may be easily adjusted to suit the requirementsof a given application, simply by placing these units appropriately.

It may also be desirable to institute a time delay between the reversalof the conducting or non-conducting condition of either electric eyeunit and the resulting roll movement, in order to avoid any correctivemovement when there is merely an edge waviness of brief length, or adiscontinuity such as a tear in the selvage of the web. These means maybe of a conventional type and are indicated only schematically at 52 inFIG. 4.

It will be understood that a single photo-cell may be used as adetector, in which case a balanced-armature relay would replace the tworelays 36 and 38. Adjustment of the width of the dead zone would be madeoptically by adjusting the spacing of the light source and photo-cellfrom the web so as to alter the width of the light beam at the plane ofthe sheet.

For a further understanding of the control characteristics of thisapparatus and of its mode of operation, some of these characteristicsare graphically compared in FIGS. 57 with those of systems which havebeen defined herein as conventional for purposes of description. In FIG.5, the principal characteristic of roll motion with respect to selvagedisplacement is shown in solid line for one type of conventional system,and in dashed line for another conventional system, the proportionaltype. In either case, it is the primary characteristic that the roll ischanging its tilt angle continuously, so long as an error persists whichis in excess of the tolerance limits LL.

In the simplest conventional method of control, a uni form angularvelocity is imparted to the roll regardless of the magnitude of theerror, and persists in the same angular sense so long as the errorremains. Thus, the angular displacement continues to increase even afterthe maximum excursion of the edge has passed and the web has begun toreturn to the normal position; the roll does not cease its angularmovement until after the error has decreased to less than the tolerancelimit. Further, the roll remains tilted at the maximum angle even whenthe edge is inside the tolerance limit, and so continues shifting thesheet toward the opposite extreme. The control system is not responsivein the dead zone, and therefore the edge must pass the oppositetolerance limit before any action is taken to return the roll towardneutral position.

The proportional control system has the characteristic that the angularvelocity imparted to the roll is proportional to the magnitude of theexcursion of the selvage beyond the tolerance limits. Again, however,the angular displacement continues at a maximum even after the error hasbeen eliminated.

In FIG. 6, the principal characteristic of the improved apparatus isshown, which is that a fixed maximum tilt angle is promptly introducedwhen an error in excess of tolerance limits occurs, without reference tothe magnitude of the error; and that the tilt angle immediately returnsto zero when the error is corrected within the tolerance limits. Theangular velocity of the tilting movement is large, and the movementterminates after a brief interval in a fixed angle of tilt. The rollthen remains in this fixed position, during which time the error willcontinually decrease; and immediately upon the return of the guided edgewithin the tolerance limits L-L, the roll is returned with a maximumangular velocity to the neutral position. The roll therefore does notremain tilted for any appreciable time interval subsequent to the actualcorrection of the deviation, and does not produce substantialover-correction.

In alternative embodiments of the invention described hereinafter, therate of tilting movement of the roll from the neutral position isintentionally reduced somewhat, to avoid over-correction of smallerrors, while the rate of return to neutral continues to be extremelyrapid The rate of change of tilt angle during the tilting movement wouldthen be less rapid than in FIG. 6, but the rate of restoring to neutralwould remain the same.

A generalized comparison of sheet-guiding actions is shown in FIG. 7, inwhich curve A represents a typical deviation of a sheet which is notbeing guided. Offset against the tendency of the sheet to wanderlaterally as in curve A, the edge position resulting from the action ofa conventional proportional-velocity system is shown by curve B, andthat produced by a typical example of the improved apparatus is shown incurve C. It is assumed in each case that the selvage is initially spacedat the center of the dead zone between tolerance limits L-L, andcommences to wander first in one lateral direction, then the other.

The conventional guider starts to respond at point :1 when the errorfirst exceeds the tolerance limit. The slope of its response curveimmediately starts to diverge from that of the unguided web as the rollstarts to tilt. The divergence of slope continues to increase until theerror re-entcrs the dead zone at point e. Within the dead zone, the rollremains fixed at a maximum angle of tilt, and consequently a severeovershoot occurs, starting at point 1. Beyond f, the divergence in slopestarts to decrease, and at g, where curve B is essentially parallel withcurve A, the roll has reached its neutral position. However, since alarge error exists, the roll continues to tilt rapidly toward theopposite corrective position. This eventually brings the edge backwithin the dead zone at point h.

The improved guider also starts to respond at a, and due to the rapidmotion of the roll, applies correction at a maximum rate at point j,which rapidly brings the error back within the dead zone at k. At thispoint the roll returns to neutral position until I is reached, whereuponthe roll again tilts, correcting the error at point m, after which thecorrective cycle repeats until point 12 is reached. From n to 0, noguiding action occurs, since the edge is within the dead zone. Frompoint to point p, another series of corrective motions of the rolloccurs, this time in the opposite lateral direction.

The characteristic of my improved apparatus is relatively free from thetendency to over-correct, because an approaching error is anticipated byshifting the roll rapidly to a fixed corrective tilt angle, andreturning it immediately to the neutral position when the sheet edge hasbeen returned once more to a path within the tolerance limits.

In use with very delicate materials, I prefer to employ a roll (notshown) having a series of independently rotatable sections spaced alongthe axle, so that each section may assume a rotational velocity inkeeping with its rapid angular movement relative to the local portion ofthe sheet. This expedient permits use of a tilt angle affording a highrate of correction with delicate materials.

The fixed angle of tilt of the guide roll may be selected of a maximumvalue consonant with the ability of a given material to withstand rapidcrawling movement without injury. However, a lesser angle would reducethe cycling frequency, with some increase in the duration of error.

Referring now to HS. 8, an alternative embodiment is shown which isadapted once again for the smaller-sized guiders, and in which pneumaticsensing and control means are employed. The position of an edge of thesheet 12 is in this case detected by a pivoted finger 6t biased lightlyby a tension spring 62, to control the escape of air pres sure throughan orifice 64 by means of a valve element 66 affixed to the finger.

Compressed air is supplied to the pressure release valve thus formed bya supply conduit 63, through a fixed orifice 70, thereby to control thepressure in an expansible chamber device 72 according to the position ofthe sheet 12. The expansible chamber device includes a flexiblediaphragm '74 whose position, being determined by the pressure obtainingwithin, is a function of the sheet position. It will be understood thata displacement of the sheet to the left as viewed in 516. 8 will openthe pressure release valve further, and result in an upward displacementin the diaphragm 74, while a displacement to the right willcorrespondingly reduce the area of the pressure release orifice anddisplace the diaphragm 74 downwardly.

In order to translate the control movements of the diaphragm intoindependent motions of the opposite ends of the roll axle 14 to beinstituted at different pressure limits, the control motion is split bymeans of a balanced link 76, which is pivotally connected at its centerby means of a rod 73 to the diaphragm. At its opposite ends, the link 76is connected to valve control rods 80 and 82, which are pivoted to thevalve cores 84 and 86 of a pair of similar three-Way control valves 88and 93*, respectively.

The valve cores may be rotated to alternate positions for admittingcompressed air to, or for exhausting, pneumatic motors 92 and 94. In thenormal position of the sheet shown, the valve 83 is set to exhaust theactuator 92, and the left-hand end of the roll axle is held in normalposition by a tension spring 96. On the other hand, the valve is set toenergize the actuator 94, holding the right-hand end of the axle innormal position against the bias of a tension spring 98. In this neutralposition, downward force is exerted by rod 78 equally on rods 89 and 82.However, the arms 84 and 86 are against their upper and lower stops,respectively; thus the spring 192 is compressed With less force than thespring ltlil. Although preloaded, the springs and 162 and diaphragm 74must have a low spring rate, so that valves 38 and 99 will be moved fromone position to the other with negligible pressure changes. Thepreloading of the springs is achieved by engaging their lower ends withadjustable stops 1% and 106, respectively, which are threadedly engagedin the support means.

Now if it is assumed that the web shows a tendency to move to the rightin FIG. 8, the pressure on the diaphragm 74 will increase to drive thecontrol rod 80 downwardly, the link 76 pivoting about the upper end ofrod 82 as a fulcrum. At a predetermined pressure corresponding to atolerance limit, and determined by the setting of the stop 194, the core84 will shift from its upper to its lower stop, admitting compressed airto the actuator 92, and immediately tilt the roll in a correctivedirection, clockwise as seen in FIG. 8. The consequent return of thesheet within the tolerance limit relaxes the diaphragm force and allowsthe spring 109 to raise the core 34 to its upper stop, exhausting theactuator 92, and the spring 96 returns the roll immediately to a neutralposition.

In the eventuality that the sheet tends to wander to the left, on theother hand, the pressure acting on the diaphragm 74 will be reduced,consequently pivoting the lever 76 counter-clockwise to relieve thecompression of the spring 162. The core 34 acts as a fulcrum, being heldin fixed position by the spring 130. As the displacement exceeds thetolerance limit, the pressure change causes the valve core 86 to beshifted to exhaust the actuator 94, and permit the spring 98 to shiftthe roll suddenly to a corrective tilted position. The consequent returnof the sheet edge to the dead zone increases the control pressuresufficiently to drive the rod 82 downwardly to re-energize le actuator94, and this returns the roll immediately to a neutral position. Thelink 76 pivots clockwise to bring about this movement, re-compressingthe spring 1&2 and acting upon the relatively compressed spring 160 as afulcrum. The movement restores the system to equilibrium in the positionshown in FIG. 8.

The tolerance limits may be adjusted by resetting the stops 104 and 106to alter the compressions of the springs Tilt) and 102, and thereby varythe level of control pressures necessary to bring about movement of thecontrol valves 88 and 99.

The values of the fixed angles of tilt of the roll in its correctivepositions may be adjusted to permit the selection of the maximum angle,and correspondingly the maximum correction rate, which is consistentwith the ability of the particular sheet material to tolerate rapidcrawling movement over the roll. This adjustment is provided for by stopabutment screws 114, threaded in suitable flanges 116 of the supportstructure 18, so as to define the terminal tilted positions of the roll.Further, these stop abutment means may be independently adjusted tocause the roll to have something other than a truly perpendicularrelation to the direction of sheet travel in its neutral position; forif there is an inherent lateral bias applied to the sheet bymisalignment of other elements of the handling equipment, as is oftenthe case, this bias can be offset by giving the roll a slight correctivetilt in its neutral position.

The embodiments which have been described utilize spring means forreturning the guide roll to the neutral position. However, in guiders oflarger sizes, the required length of the return stroke and the actuatingforces involved will not permit the use of a spring return, since therestoring force of a spring varies in proportion of the displacement,and the return movement would be unduly delayed. The embodimentsillustrated in FIGS. 9-13 utilize double-acting motors to apply uniformrestoring as well as displacing forces to the guide roll, thus assuringa minimum time lag in the return movement and the least over-correction.

In FIG. 9, a system is shown in which the actuating rods 136 ofpneumatic double-acting motors 130 terminate in eyes 138 for drivingconnection with the opposite ends of the axle 14. These motors are underthe control of a spool valve 140, whose double spool 142 is connected bya pivot 148 to a finger 146; the latter is pivotally mounted on a fixedpad 159 for detecting the position of an edge of the traveling sheet 12.To clarify the drawing, the ha er 146 is shown in a position upstream ofthe roll 10; however, it is preferred to place the detector downstream,so that the effect of the guiding action is fed back to the detector anda closed loop system of control is provided. In the neutral positionshown, the spool 142 exhausts each of the motors 130 through conduits153 or 169 and exhaust ports 162 or 164. Compressed air is suppliedthrough a branched conduit 152 to the spool valve and also to a pressureregulator 154; the latter is set to supply air at one-half the supplypressure to each of the motors 13% through a branched conduit 156. Theair so supplied urges the pistons 134 in a direction to hol he uide roll16 in the neutral position shown. In the event that the sheet changesits lateral position sufliciently to shift the spool 142 so as tocommunicate either of the conduits 158 or 166 with the air supplyconduit 152, the full supply pressure is applied to the piston 134 ofthe corresponding motor 139, in opposition to the half-pressure appliedto the opposite face of the piston. The motor which is so supplied thendrives the connected end of the roll 11) to a tilted position forcorrecting the sheet deviation. Return or" the sheet to its originalpath re-establishes the neutral relationship illustrated, byreconnecting the actuated motor to exhaust.

In FIG. 10, a modification of the spool valve 14 is shown. in whichprovision is made for adjusting the tolerance limits within whichdeviation of the sheet edge is permitted without guider response. Thelength of the dead zone between the tolerance limits is determined bythe difference between the spacing b between the conduits 15S and 169,and the spacing a between the spool elements 178. The spool is formed intwo segments 163 and 170, one of them incorporating a threaded male stud1'74, and the other having a threaded female socket 172 so that thespacing a may be adjusted. A set screw 176 is provided to secure theparts in adjusted relation.

In FIG. 11, a modification of the control system of FIG. 9 is shownwhich delays tilting movement of the guide roll from the neutralposition without reducing the rate of restoration. Adjustablerestrictions 182, comprising needle valves, are interposed in theconduits 15S and 160 to limit the rate of pressurized fluid flow fro .1the valve 149 to the motors 131), thus serving to reduce the rate oftilting movement. However, the restrictions are by-passed for returnflow to exhaust the motors, by means 1d of branches 184 interposed inthe conduits 158 and 160, and each having a one-way check valve 186.

The control system in FIG. 11 provides a rate of tilting movement whichis slower than the rate of return, so that the maximum angle of tilt isnot fully assumed when very small errors arise and disappear rapidly.However, if an error persists over a relatively long interval,indicating that it does have a more substantial magnitude, the rollarrives at the fully tilted position after a brief interval, and thepreviously-explained advantages of anticipating the extent of errors arelargely realized. At the same time, any tendency to over-correct thefrequently-occurring small errors is reduced. And since the rate ofrestoration of the roll to neutral is unaffected, any tendency toovercorrect by delaying the return movement is avoided, just as in thepreceding embodiment.

The system illustrated in FIG. 12 reduces the lag in control responsestill further in that the spools 202 of control valves 190 are driven bythe cores 286 of quickacting solenoids 204. The solenoids are under thecontrol of a sheet edge sensing finger 283, which serves, upon a shiftof the sheet 12 in either lateral direction, to energize an appropriateone of the solenoids 2154 through a lead 213, one of a pair of contacts210, and a corresponding one of leads 214. The tolerance limits arereadily adjustable by varying the spacing between the contacts 21%.

In this form a control valve 199 is provided for each double-actingactuator 13%. When neither solenoid 294 is energized, and both spools292 are raised, the roll 16 is held in a neutral position by compressedair supplied by a branched conduit 192, through each of the valves 1%and conduits 2%, to the motors 130. The upper chamer of each motor thenexhausts through a conduit 198 and an exhaust port 191.

In the position of the parts shown in the drawing, the sheet 12 hasdrifted to the right, energizing the righthand solenoid, and thusdrawing the spool of the corresponding control valve downwardly.Pressure for tilting the right-hand end of the roll is supplied througha restriction 196, comprising an adjustable needle valve, a branchedconduit 194, the right'hand spool valve, and a conduit 1%, to the upperchanioer of the right-hand actuator 130. The lower chamber of the motoris exhausted through the conduit 2% and the right-hand spool valve.

It is to be noted that in this embodiment the rate of pressure fluidsupply, for drivin the actuators in a direction to tilt the roll, isrestricted by the valve 196; therefore the rate of tilting movement ofthe roll 1i; is rather less than the rate of restoring movement toneutral, since the latter is brought about with a full rate of flow ofpressure fluid. Essentially the same considerations apply as werepreviously raised relative to FIG. 11.

A guider is shown in FIG. 13 in which one end of the roll axle 14 issupported in a fixed pivot 211, and the other is free to slide betweenthe neutral position shown, and two limiting tilted positions ofopposite sense, in an elongated slot 16 formed in the frame 13. Adoubleacting actuator 215 has its piston 214 drivingly connected withthe free end of the roll axle by means of an arm 212, which bears a leg213 on which is mounted the double spool 218 of a servo-control valve215. Compressed air is supplied by a suitable. source to the center ofthe valve 215 through a conduit The valve 215 maintains control onlywhile the sheet 12 continues in its proper path. If the roll 16 and thepiston 214 tend to become displaced from the centralized or neutralposition, the corresponding displacement of the spool 218 to right orleft admits air through one of a pair of conduits 226 and valves V1 orV2, which are at this time de-energized, to a corresponding one ofconduits 224, thus to recentralize the piston 214 and restore the rollto the neutral position. The unpressurized chamber of the motor 216 isexhausted to atmosphere through 1 1 its associated conduits 224 and2.26, tie-energized valve V1 or V2, and an exhaust port 226 in acorresponding end of the servo-control valve 215.

In the event of a displacement of the sheet 12 from its normal path, thevalves V1 and V2 serve to transfer control of the apparatus from theservo-valve 215 to an appropriate one of solenoid valves V3 or v4, foractuating the motor 216 in a sense to tilt the roll 19 as required torestore the sheet to its proper path. The valves V1, V2, V3 and V4 areall under the control of an edge-position sensing linger 249, pivotallymounted on a fixed pad 242. and supplied from a suitable electric powersource by a lead 238. A lateral movement of the sheet edge closes one ofeach of two pairs of contacts 234 and 236, the latter pair being shortedby a jumper 235. Closure of either contact 236 energizes the coils 238of both solenoid valves V1 and V2, thus closing communication betweenthe conduits 224- and 226, opening the conduits 22.4 to communicatingpiping 223 for control of the motor 2.16 by the valves V3 and V4.Depending upon the direction of sheet edge translation, one of thecontacts 23% is also closed to energize the coil 232 of a correspondingsolenoid valve V3 or V4, opening the corresponding piping 228 to asuitable compressed air supply, and ciosin g its normal connection toexhaust. One chamber of the motor 216 is thus supplied with pressurefluid through one of the sets of valves Vll, V3, or V2, V4, while theother chamber is exhausted to atmosphere. The roll ill is therebyshifted to a terminal tilted position, causing the sheet to translate toits original path; restoration opens the contacts previously closed bythe finger 24d, and restores control to the servo-valve 215, whichimmediately re-centers the motor 216 and the roll 10.

While I have illustrated an described preferred embodiments of myinvention by Way of illustration, it will be understood by those skilledin the art that various changes and modifications may be made thereinwithout departing from the true spirit and scope of the invention, whichI therefore intend to define in the appended claims without limitationto the details of the illustrated embodirnents.

What I claim is:

1. Sheet guiding apparatus comprising at least one roll arranged toengage a traveling sheet of material transversely to the direction oftravel;

control means including edge position sensing means arranged in spacedrelation to an edge of the sheet and responsive to lateral deviation ineither lateral direction in excess of a predetermined permissabletolerance to produce a control signal indicative of the direction of thedeviation;

means supporting each end of said roll for independent displacement topermit limited tilting movement of said roll, from a neutral transverseposition with respect to the direction of travel of said sheet, toeither of two predetermined tilted positions of opposite angular sense,to induce a tendency in the sheet to correct the lateral position of itspath of movement;

a pair of actuating means one drivingly connected with each end of saidroll for inducing tilting movement and restoring movement thereofbetween said neutral position and either of said tilted positions, andeach connected with said control means for independent energizationthereby in a sense to induce tilting movement, one in response todeviation in each lateral direction, without reference to the magnitudeof a signalled deviation;

each of said actuating means being constructed and arranged to tilt saidroll to a corrective one of said predetermined tilted positionsimmediately upon energization by said sensing means and to retain saidroll fixed in said one position during the continuance of saiddeviation, and to return said roll with a snap action immediately to theneutral trans- Cir verse position upon discontinuance of a signalleddeviation. 2. Sheet guiding apparatus as recited in claim 1, in whichsaid actuating means comprise a pair of doubleacting motive meansconstructed and arranged to apply a uniform driving force to said rollthroughout the tilting and restoring movements.

3. Sheet guiding apparatus as recited in claim 1, in which each of saidactuating means comprises a singleacting motive means constructed andarranged for inducing tilting movement of one end of said roll, andmeans biasing said one end of said roll toward said neutral position.

4. Sheet guiding apparatus comprising at least one roll arranged toengage a traveling sheet of material transversely to the direction oftravel;

control means including sensor means arranged in a fixed position alongthe path of movement of the traveling sheet and sensitive to any lateraldeviation of said sheet from a predetermined path in excess of apredetermined permissable tolerance, for producing a control signalindicative of the sense of the excessive deviation; means supportingsaid roll for limited tilting movement from a neutral transverseposition with respect to the direction of travel of said sheet to eitherof two predetermined limiting tilted positions of opposite angular senseto induce a tendency in the sheet to correct the lateral position of itspath of movement;

double-acting actuating means drivingly connected with said roll forinducing tilting movement and restoring movement thereof between saidneutral position and either of said tilted positions, and connected withsaid control means for energization by a control signal generatedthereby without reference to the magnitude of the signalled deviation;

said actuating means being constructed and arranged to apply a uniformdriving force to tilt said roll to one of said tilted positionscorresponding to the sense of the excessive deviation immediately uponenergization by a control signal, to retain said roll fixed in said onetilted position during the continuance of said signal, and to apply auniform driving force to return said roll immediately with a snap actionto the neutral transverse position upon discontinuance of said signal.

5. Sheet guiding apparatus as recited in claim 4, in which one end ofsaid roll is mounted in a fixed pivot; said double-acting actuatingmeans being drivingly connected with the other end of said roll andmovable between a centralized position holding said roll in the neutralposition, and two roll-tilting positions of opposite senses; saidcontrol means comprising a servo-control valve having a valve elementdrivingly connected with said actuating means and normally connected forcontrol of said actuating means to maintain said roll in the neutralposition, together with by-oass valve means connected for energizationby a control signal generated by said sensor means to int rruptconnection of said servo-control valve with said actuating means, saidby-pass valve means being constructed and arranged upon energization tocontrol said actuating means for tilting said roll to a corrective oneof said tilted positions.

6. Sheet guiding apparatus as recited in claim 4, said actuating meanscomprising double-acting fluid motors each having two opposed expansiblechambers; together with pressurized-fluid supply means, andpressure-reducing means connecting said supply means to deliver fluid atreduced pressure continuously to first chambers of each of said motorsfor biasing each end of said roll toward the neutral position; saidcontrol means including a control valve normally connecting secondchambers of each of said motors to exhaust, and selectively movable inresponse to a control signal to admit fluid from said supply at fullpressure to the second chamber of either of said 13 motorsalternatively, as required to induce a corrective tilting movement.

7. Sheet guiding apparatus as recited in claim 4, in which saidactuating means comprise fluid motors; and said control means includes acontrol valve having a double spool element, pressure-fluid supplymeans, and a pair of conduit means selectively communicable with saidsupply means by movement of said double spool element, for supplyingpressure fluid to either selected one of said motors; such that saidtolerance limit is determined by the diflerence between the spacingbetween said conduit mean-s and the spacing between the spools of saiddouble spool element; said spool element being constructed and arrangedfor adjustment of the spacing between the spools thereof, for adjustingsaid tolerance limit.

8. Sheet guiding apparatus as recited in claim 4, in which said controlmeans and said actuating means are constructed and arranged to inducetilting movement of said roll at a lesser rate than the restoringmovement.

9. Sheet guiding apparatus as recited in claim 4, in which saidactuating means comprise fluid motors; and said control means includescontrol valve means, pressure fluid supply means, and conduit meansselectively communicable with said supply means by said control valvemeans to supply pressure fluid to a selected one of said motors to tiltthe connected end of said roll, said conduit means being simultaneouslyconnected by said control valve means to return pressure fluid from theother of said motors to exhaust; said conduit means including flowrestriction means for limiting the rate of flow of pressure fluid tosaid motors, and including unrestricted one-way by-pass return means foran increased rate of return flow.

10. Sheet guiding apparatus comprising at least one roll arranged toengage a traveling sheet of material transversely to the direction oftravel;

detection means comprising edge position sensing means arranged inspaced relation to an edge of the sheet and responsive to lateraldeviation in either lateral direction in excess of a predeterminedpermissable tolerance to produce a control signal indicative of thedirection of the deviation;

means supporting each end of said roll for independent displacement topermit limited tilting movement of said roll, from a normal transverseposition with respect to the direction of travel of said sheet, toeither of two predetermined limiting positions of opposite angularsense, to induce a tendency in the sheet to correct the lateral positionof its path of movement;

a pair of actuators one drivingly connected with each end of said rollfor inducing tilting movement thereof between said normal position andeither of said limiting positions, and each connected with said sensingmeans for independent energization thereby, one in response to deviationin each lateral direction, without reference to the magnitude of asignalled deviation;

means biasing each end of said roll toward said normal position forreturning said roll irrunediately thereto upon de-energization of saidactuators;

each of said actuators being constructed and arranged to tilt said rollwith a snap action to a corrective one of said predetermined limitingposition-s immediately upon energization by said sensing means and toretain said roll fixed in said one position during the continuance ofsaid deviation, and said biasing means being constructed and arranged toreturn said roll with a snap action immediately to the normal transverseposition upon de-energization of said actuators by discontinuance ofsaid deviation.

11. Sheet guiding apparatus comprising at least one roll arranged toengage a traveling sheet of material transversely to the direction oftravel;

detection means including a sensor arranged in a fixed position alongthe path of movement of the traveling sheet and sensitive to any lateraldeviation of said sheet from a predetermined path to produce an errordetection signal, and transducer means for translating said errordetection signal into separate control signals one indicative of thesense of a deviation in excess of a predetermined permissable tolerancelimit in either lateral direction;

means supporting said roll for limited tilting movement from a normaltransverse position with respect to the direction of travel of saidsheet to either of two predetermined limiting positions of oppositeangular sense, to induce a tendency in the sheet to correct its path ofmovement;

a pair of actuators one drivingly connected with either end of said rollfor inducing tilting movement thereof between said normal position andeither of said limting positions, and connected with said transducermeans for independent energization each by one of said control signalswithout reference to the magnitude of the signalled deviation;

means biasing each end of said roll toward said normal position forreturning said roll immediately thereto upon de-energization of saidactuators;

each of said actuators being constructed and arranged to tilt said rollwith a snap action to a corrective one of said predetermined limitingpositions immediately upon energization by a control signal and toretain said roll fixed in said one position during the continuance ofsaid signal, and said biasing means being constructed and arranged toreturn said roll immediately with a snap action to the normal transverseposition upon de-energization by discontinuance of said signal.

References Cited UNITED STATES PATENTS 2,914,957 12/1959 Johnson 226 23X 3,043,153 7/1962 Hindle etal 226-21 X FOREIGN PATENTS 834,014 5/1960Great Britain.

ALLEN N. KNOWLES, Primary Examiner.

